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RE: QRD diffuser, 1D or 2D best?

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In Reply to: RE: QRD diffuser, 1D or 2D best? posted by johnvb on November 23, 2012 at 05:52:48

People usually use the 1-D QRD's. I'm not sure what would happen to the sound if you used the 2-D's. Line sources have as one of their advantages the ability to cancel out the floor and ceiling and approximate an infinite line source, so I've always figured it was best not to spray randomized reflections there. But this is purely speculative, I don't know of anyone who's tried it.

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RE: QRD diffuser, 1D or 2D best? - johnvb 16:56:43 11/23/12 (7)
Hey Josh. From pics posted on the internet that I have found of Maggie listening room, I agree, they all have 1Ds. But I chalked it up to the apparent fact that there are a lot more commercially available 1Ds then 2Ds.

Seems like the 2D pics are more often then not in recording/mixing studios, whatever that means. Even though the 2ds would be more labor intensive, I think the diy end product could look better then a diy 1D. But if made from wood, the 2D definitely would be heavier, which could be a problem when mounted to my hollow core doors.

I know nothing on this subject, but if the diffusers are to reduce comb filtering(?) of the back wave vs front wave, then I would think the 2Ds, bouncing the back wave in all four directions, would achieve that goal more easily.
- RE: QRD diffuser, 1D or 2D best? - josh358 17:32:50 11/23/12 (6)
  As you point out, a 2D diffuser should reduce the amplitude of the first reflection more than a 1D diffuser. That would likely make it more effective at its primary goals but not necessarily, since it involves psychoacoustics and the sense of depth is related to reverberation levels. (The relationship between delay and level is a somewhat complex one.) Also, as I said, you're also spraying sound at the floor and ceiling, which could negate one of the main advantages of line sources.
  
  I don't think you can extrapolate from what's done in some recording studios -- recording studios have a different acoustic than what you want at home and line source dipoles react very differently with the room than boxes.
  
  I don't think a QRD diffuser is any lighter than a skyline, they're basically the same thing except that the skyline is patterned in two dimensions.
  
  I'd suggest at this point that you ask the guys at the diffuser makers what they recommend, either directly or on one of the acoustics forums. If anyone has had experience with line sources and 2D diffusers, it's them. I'd be curious to know what you find out.
  - RE: QRD diffuser, 1D or 2D best? - Satie 10:59:57 11/24/12 (1)
    I would not dare mess with the vertical dimension off of line sources since that is where height cues unique to this kind of speaker come from. Diffusing those is a clear no-no, so no 2D.
    - RE: QRD diffuser, 1D or 2D best? - josh358 11:20:42 11/24/12 (0)
      That's my concern. If the 2D diffuser ran floor to ceiling, it might not matter, since the diffuser itself would be reflected to approximate an infinite line. But that isn't the case. I don't know if this would be aurally significant but to my way of thinking, while it's something that might be interesting to experiment with, it's a lot safer to go with the tried-and-true 1D diffusers.
  - RE: QRD diffuser, 1D or 2D best? - johnvb 19:37:17 11/23/12 (3)
    Yeah, I'll run it by the guys on the Acoustic Circle. On another thread I started over there, I recall you mentioned you were playing around with some GIK gridfusors. How's that working out, good product?
    - RE: QRD diffuser, 1D or 2D best? - josh358 19:49:00 11/23/12 (2)
      They're very lightweight so good for my application, which is hanging on my fireplace mantle. But for your application, I think you want wood, which since it's denser is more effective at low frequencies and has I think more euphonic resonances, and is also more robust (since you're mounting them on doors).
      - RE: QRD diffuser, 1D or 2D best? - johnvb 05:09:30 11/25/12 (1)
        
        In Reply to: RE: QRD diffuser, 1D or 2D best? posted by josh358 on November 23, 2012 at 19:49:00
        
        Looks like the consensus is 1D, so I will go with that. Does make sense that one would want as little reflections as possible bouncing around on the ceiling and floor. I can make the diffusors that go on the door out of wood. If too heavy I'll design them on hinges, to be hung on the outside door jambs, like a screen door would.
        If I feel I also need some on my bass trap (I started that Planar Circle thread regarding that subject), I'll spring for the GIK gridfusors. Thanks again.
        
        Edits: 11/25/12
        
        RE: QRD diffuser, 1D or 2D best? - josh358 05:30:52 11/25/12 (0)
        
        In Reply to: RE: QRD diffuser, 1D or 2D best? posted by johnvb on November 25, 2012 at 05:09:30
        
        If you're putting them in the corners, you might want to go for the corner second reflections (speaker to front wall to side wall to ears). In my experience, that tends to make the sound wrap around the side walls. I think you could get away with treating only the first reflection point on the front wall.
        
        This isn't something I've tried, just something I've wondered about . . .

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